Estudo de fenômenos de corrosão no aço UNS S41003 soldado pelo processo MIG

Abstract

The aim of this study was to investigate how MIG (metal inert gas) welding impacts the corrosion resistance properties of UNS S41003 steel. The welds were performed with two energy levels. After welding, microstructural characterization, tensile, Vickers microhardness, ferritoscopy, and potentiodynamic polarization tests, were performed. Stress corrosion crack (SCC) and double-loop polarization (DL-EPR) tests were also carried out. From the potentiodynamic polarization tests, a lower pitting potential was observed in the heat affected zone (HAZ) of both welds: high energy weld (HE) and low energy weld (LE). A pronounced ferrite grain growth was observed in the HAZ of the welds, with the presence of martensite needles in their grain boundaries. In the fused zone (FZ), the microstructure was constituted by austenite, derived from the filler metal (AISI 309LSi), with islands of delta ferrite derived from the dilution of the base metal (UNS S41003). The HAZ exhibited lower pitting potential values compared to the BM. High values of ir/ia were found in the FZ, BM, and HAZ, indicating susceptibility to intergranular corrosion. Greater susceptibility to stress corrosion cracking (SCC) was evidenced in the HAZ compared to the FZ and BM.